/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.Graphs.checkNonNegative;

import com.google.common.annotations.Beta;
import com.google.common.base.Optional;

/**
 * A builder for constructing instances of {@link MutableValueGraph} with user-defined properties.
 *
 * <p>
 * A graph built by this class will have the following properties by default:
 *
 * <ul>
 * <li>does not allow self-loops
 * <li>orders {@link Graph#nodes()} in the order in which the elements were added
 * </ul>
 *
 * <p>
 * Example of use:
 *
 * <pre>
 * {
 *     &#64;code
 *     MutableValueGraph<String, Double> graph = ValueGraphBuilder.undirected().allowsSelfLoops(true).build();
 *     graph.putEdgeValue("San Francisco", "San Francisco", 0.0);
 *     graph.putEdgeValue("San Jose", "San Jose", 0.0);
 *     graph.putEdgeValue("San Francisco", "San Jose", 48.4);
 * }
 * </pre>
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @since 20.0
 */
@Beta
public final class ValueGraphBuilder<N, V> extends AbstractGraphBuilder<N> {

    /** Creates a new instance with the specified edge directionality. */
    private ValueGraphBuilder(boolean directed) {
        super(directed);
    }

    /** Returns a {@link ValueGraphBuilder} for building directed graphs. */
    public static ValueGraphBuilder<Object, Object> directed() {
        return new ValueGraphBuilder<Object, Object>(true);
    }

    /** Returns a {@link ValueGraphBuilder} for building undirected graphs. */
    public static ValueGraphBuilder<Object, Object> undirected() {
        return new ValueGraphBuilder<Object, Object>(false);
    }

    /**
     * Returns a {@link ValueGraphBuilder} initialized with all properties queryable from {@code
     * graph}.
     *
     * <p>
     * The "queryable" properties are those that are exposed through the {@link ValueGraph}
     * interface, such as {@link ValueGraph#isDirected()}. Other properties, such as
     * {@link #expectedNodeCount(int)}, are not set in the new builder.
     */
    public static <N> ValueGraphBuilder<N, Object> from(ValueGraph<N, ?> graph) {
        return new ValueGraphBuilder<N, Object>(graph.isDirected()).allowsSelfLoops(graph.allowsSelfLoops())
                .nodeOrder(graph.nodeOrder());
    }

    /**
     * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
     * Attempting to add a self-loop to a graph that does not allow them will throw an
     * {@link UnsupportedOperationException}.
     */
    public ValueGraphBuilder<N, V> allowsSelfLoops(boolean allowsSelfLoops) {
        this.allowsSelfLoops = allowsSelfLoops;
        return this;
    }

    /**
     * Specifies the expected number of nodes in the graph.
     *
     * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
     */
    public ValueGraphBuilder<N, V> expectedNodeCount(int expectedNodeCount) {
        this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
        return this;
    }

    /** Specifies the order of iteration for the elements of {@link Graph#nodes()}. */
    public <N1 extends N> ValueGraphBuilder<N1, V> nodeOrder(ElementOrder<N1> nodeOrder) {
        ValueGraphBuilder<N1, V> newBuilder = cast();
        newBuilder.nodeOrder = checkNotNull(nodeOrder);
        return newBuilder;
    }

    /**
     * Returns an empty {@link MutableValueGraph} with the properties of this
     * {@link ValueGraphBuilder}.
     */
    public <N1 extends N, V1 extends V> MutableValueGraph<N1, V1> build() {
        return new ConfigurableMutableValueGraph<N1, V1>(this);
    }

    @SuppressWarnings("unchecked")
    private <N1 extends N, V1 extends V> ValueGraphBuilder<N1, V1> cast() {
        return (ValueGraphBuilder<N1, V1>) this;
    }
}
